Acute porphyrias are inherited metabolic disorders that cause life-threatening neurological symptoms, and are treated with intravenous heme. The objective is to study tin mesoporphyrin (an inhibitor of heme degradation) for enhancing the effects of heme therapy in these disorders. The specific aims are to determine 1)the optimal dose combinations of tin mesoporphyrin and heme for reducing porphyrin precursor levels in stable patients with acute intermittent porphyria; 2)safety and efficacy of tin mesoporphyrin when given with heme in acture attacks of porphyria 3)safety and efficacy of tin mesoporphyrin for decreasing the frequency heme infusions needed to prevent attacks of porphyria. Heme albumin may be substituted if the supply of heme areginate is limited. Tin mesoporphyrin is likely to be approved for treatment of neonatal jaundice, and will become available for use in porphyria as well. Therefore it is important to know if, as suggested by preliminary reports, it is safe an effective in porphyria and the optimal dosage. The studies will determine whether tin mesoporphyrin is safe and effective and thereby addresses an important management option for patients with acute porphyrias in the U.S.